The proposed research aims to characterize ultrastructural alterations which occur in certain renal cells after treatment with vinblastine sulfate, an oncolytic drug which causes depolymerization of cytoplasmic microtubules. Included in this study are: (1) experiments to elucidate what effect microtubule loss has on two functions frequently ascribed to cytoplasmic microtubules, namely cell-shape maintenance and translocation of other cell organelles, and (2) experiments designed to demonstrate whether endothelial detachment occurs within vessels of the kidney and other organs after intravenous administration of vinblastine. In addition, it is proposed that the feasibility be explored of using isolated fish nephrons as a model system to study and define the importance of intact microtubules, microfilaments, cell junctions, and basement membrane in maintaining the normal branched shape of renal podocytes. The proposed research project involves use of the techniques of cytochemistry, stereomicroscopy, scanning electron microscopy, freeze-etching, and routine transmission electron microscopy.